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[PATCH v9] revision.c: implement --max-count-oldest

From
Junio C Hamano <gitster@pobox.com>
Date
Jun 1, 2026, 21:53 UTC
Message-ID
<xmqq4ijm3p2x.fsf@gitster.g>
In-Reply-To
<ag3kJ_xKY6584De4@exploit>
Mirko Faina <mroik@delayed.space> writes:
Show 10 quoted lines
> On Wed, May 20, 2026 at 03:02:34PM +0900, Junio C Hamano wrote:
>> 
>> This breaks CI
>> 
>>   https://github.com/git/git/actions/runs/26138986677/job/76880268854#step:4:2072
>> 
>> Squash something like this to fix.
>>  ...
>
> Sorry about that. And thank you for the fix.

It has been a while, and we saw no further comments by other reviewers.

Perhaps we should declare a victory and mark the topic for 'next'.
------ >8 ------
From: Mirko Faina <mroik@delayed.space>
Date: Tue, 19 May 2026 02:55:22 +0200

"--max-count" is a commit limiting option and sets a maximum amount of commits to be shown. If a user wants to see only the first N commits of the history (the oldest commits) they'd have to do something like

    git log $(git rev-list HEAD | tail -n N | head -n 1)
This is not very user-friendly.
Teach get_revision() the --max-count-oldest option.
Signed-off-by: Mirko Faina <mroik@delayed.space>
[jc: fixed up t4202 <xmqq7boy4o05.fsf@gitster.g>]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/rev-list-options.adoc |   5 +-
 revision.c                          | 111 +++++++++++++++++++++++++++-
 revision.h                          |   2 +
 t/t4202-log.sh                      |  40 ++++++++++
 4 files changed, 154 insertions(+), 4 deletions(-)
diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc
index 2d195a1474..e8c88d0f1c 100644
--- a/Documentation/rev-list-options.adoc
+++ b/Documentation/rev-list-options.adoc
@@ -16,7 +16,10 @@ ordering and formatting options, such as `--reverse`.
 `-<number>`::
 `-n <number>`::
 `--max-count=<number>`::
-	Limit the output to _<number>_ commits.
+	Limit the output to the first _<number>_ commits that would be shown.
+
+`--max-count-oldest=<number>`::
+	Limit the output to the last _<number>_ commits that would be shown.
 
 `--skip=<number>`::
 	Skip _<number>_ commits before starting to show the commit output.
diff --git a/revision.c b/revision.c
index 599b3a66c3..5d53db3152 100644
--- a/revision.c
+++ b/revision.c
@@ -2339,10 +2339,28 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	}
 
 	if ((argcount = parse_long_opt("max-count", argv, &optarg))) {
+		if (revs->max_count_type == 1)
+			die_for_incompatible_opt2(1, "--max-count", 1,
+						  "--max-count-oldest");
 		revs->max_count = parse_count(optarg);
 		revs->no_walk = 0;
+		revs->max_count_type = 0;
 		return argcount;
+	} else if ((argcount = parse_long_opt("max-count-oldest", argv, &optarg))) {
+		if (revs->max_count_type == 0 && revs->max_count != -1)
+			die_for_incompatible_opt2(1, "--max-count", 1,
+						  "--max-count-oldest");
+		if (revs->skip_count > 0)
+			die_for_incompatible_opt2(1, "--skip", 1,
+						  "--max-count-oldest");
+		revs->max_count = parse_count(optarg);
+		revs->no_walk = 0;
+		revs->max_count_type = 1;
+		revs->max_count_stage = 0;
 	} else if ((argcount = parse_long_opt("skip", argv, &optarg))) {
+		if (revs->max_count_type == 1)
+			die_for_incompatible_opt2(1, "--skip", 1,
+						  "--max-count-oldest");
 		revs->skip_count = parse_count(optarg);
 		return argcount;
 	} else if ((*arg == '-') && isdigit(arg[1])) {
@@ -4521,15 +4539,91 @@ static struct commit *get_revision_internal(struct rev_info *revs)
 	return c;
 }
 
+static void retrieve_oldest_commits(struct rev_info *revs,
+				    struct commit_list **queue)
+{
+	struct commit *c;
+	int max_count = revs->max_count;
+	int queuei_count = 0;
+	int queueo_count = 0;
+	struct commit_list *queueo = NULL;
+	struct commit_list *queuei = NULL;
+	struct commit_list *reversed_queue = NULL;
+	struct commit_list *p;
+
+	revs->max_count = -1;
+	while ((c = get_revision_internal(revs))) {
+		/*
+		 * We need to reset SHOWN status otherwise --graph breaks.
+		 * It is fine to do, get_revision_internal() doesn't consider
+		 * children commits as they have been already processed and the
+		 * traversal happens only child to parent.
+		 *
+		 * We do this because the --graph machinery relies on the status
+		 * of the parents to decide how the printing will happen.
+		 *
+		 * We can't simply replace this instruction with a
+		 * graph_update() as it doesn't do the actualy printing, we'd
+		 * have to remove any commit that goes over the
+		 * --max-count-oldest limit from revs->graph.
+		 */
+		c->object.flags &= ~(SHOWN | CHILD_SHOWN);
+		commit_list_insert(c, &queuei);
+		if (!(c->object.flags & BOUNDARY))
+			queuei_count++;
+		while (queuei_count + queueo_count > max_count) {
+			if (!queueo_count) {
+				while ((c = pop_commit(&queuei))) {
+					commit_list_insert(c, &queueo);
+					queueo_count++;
+				}
+				queuei_count = 0;
+			}
+			c = pop_commit(&queueo);
+			queueo_count--;
+			/* We need to do this otherwise we'll discard the
+			 * commits that go over the --max-count-oldest limit but
+			 * not their respective boundaries. This matters only if
+			 * we're discarding the commit right before the boundary.
+			 */
+			for (p = c->parents; p; p = p->next)
+				p->item->object.flags &= ~CHILD_SHOWN;
+		}
+	}
+
+	while ((c = pop_commit(&queueo)))
+		commit_list_insert(c, &reversed_queue);
+	while ((c = pop_commit(&queuei)))
+		commit_list_insert(c, &queueo);
+	while ((c = pop_commit(&queueo)))
+		commit_list_insert(c, &reversed_queue);
+
+	while ((c = pop_commit(&reversed_queue)))
+		commit_list_insert(c, queue);
+}
+
 struct commit *get_revision(struct rev_info *revs)
 {
 	struct commit *c;
 	struct commit_list *reversed;
+	struct commit_list *queue = NULL;
+	struct commit_list *p;
+
+	if (revs->max_count_type == 1 && !revs->max_count_stage) {
+		retrieve_oldest_commits(revs, &queue);
+		commit_list_free(revs->commits);
+		revs->commits = queue;
+		revs->max_count_stage = 1;
+	}
 
 	if (revs->reverse) {
 		reversed = NULL;
-		while ((c = get_revision_internal(revs)))
-			commit_list_insert(c, &reversed);
+		if (revs->max_count_type == 1)
+			while ((c = pop_commit(&revs->commits)))
+				commit_list_insert(c, &reversed);
+		else
+			while ((c = get_revision_internal(revs)))
+				commit_list_insert(c, &reversed);
 		commit_list_free(revs->commits);
 		revs->commits = reversed;
 		revs->reverse = 0;
@@ -4543,7 +4637,18 @@ struct commit *get_revision(struct rev_info *revs)
 		return c;
 	}
 
-	c = get_revision_internal(revs);
+	if (revs->max_count_stage) {
+		c = pop_commit(&revs->commits);
+		if (c) {
+			c->object.flags |= SHOWN;
+			if (!(c->object.flags & BOUNDARY))
+				for (p = c->parents; p; p = p->next)
+					p->item->object.flags |= CHILD_SHOWN;
+		}
+	} else {
+		c = get_revision_internal(revs);
+	}
+
 	if (c && revs->graph)
 		graph_update(revs->graph, c);
 	if (!c) {
diff --git a/revision.h b/revision.h
index 584f1338b5..e157463cb1 100644
--- a/revision.h
+++ b/revision.h
@@ -309,6 +309,8 @@ struct rev_info {
 	/* special limits */
 	int skip_count;
 	int max_count;
+	unsigned int max_count_type:1;
+	unsigned int max_count_stage:1;
 	timestamp_t max_age;
 	timestamp_t max_age_as_filter;
 	timestamp_t min_age;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 05cee9e41b..75edb0eb38 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1882,6 +1882,46 @@ test_expect_success 'log --graph with --name-status' '
 	test_cmp_graph --name-status tangle..reach
 '
 
+test_expect_success 'log --max-count-oldest=3 --oneline' '
+	test_when_finished rm expect &&
+	git log --oneline | tail -n3 >expect &&
+	git log --oneline --max-count-oldest=3 >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --max-count-oldest=3 --reverse --oneline' '
+	test_when_finished rm expect &&
+	git log --oneline --reverse | head -n3 >expect &&
+	git log --oneline --max-count-oldest=3 --reverse >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --max-count-oldest with --max-count' '
+	test_when_finished rm stderr &&
+	test_must_fail git log --max-count-oldest=3 --max-count=3 2>stderr &&
+	test_grep "cannot be used together" stderr
+'
+
+test_expect_success 'log --max-count-oldest with --skip' '
+	test_when_finished rm stderr &&
+	test_must_fail git log --max-count-oldest=3 --skip=1 2>stderr &&
+	test_grep "cannot be used together" stderr
+'
+
+test_expect_success 'log --max-count-oldest=1000 --graph --boundary' '
+	test_when_finished rm expect actual &&
+	git log --graph --boundary >expect &&
+	git log --max-count-oldest=1000 --graph --boundary >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --oneline --graph --boundary --max-count-oldest=1' '
+	test_when_finished rm -f actual &&
+	git log --oneline --graph --boundary --max-count-oldest=1 \
+		HEAD~1..HEAD >actual &&
+	test_line_count = 2 actual
+'
+
 cat >expect <<-\EOF
 * reach
 |

-- 
2.54.0-514-g9d901a57fc
Previous: Mirko FainaNext: Mirko Faina
Message 54 of 63 in “revision.c: implement --reverse=before for walks”
  1. revision.c: implement --reverse=before for walksMirko Faina, Apr 18, 2026
  2. Tian YuchenApr 18, 2026
  3. Mirko FainaApr 18, 2026
  4. Mirko FainaApr 18, 2026
  5. Junio C HamanoApr 20, 2026
  6. Tian YuchenApr 20, 2026
  7. Mirko FainaApr 20, 2026
  8. Ben KnobleApr 19, 2026
  9. Mirko FainaApr 19, 2026
  10. D. Ben KnobleApr 19, 2026
  11. Mirko FainaApr 19, 2026
  12. Jeff KingApr 20, 2026
  13. Mirko FainaApr 20, 2026
  14. Mirko FainaApr 20, 2026
  15. Jeff KingApr 21, 2026
  16. D. Ben KnobleApr 22, 2026
  17. Mirko FainaApr 22, 2026
  18. Jeff KingApr 20, 2026
  19. Mirko FainaApr 20, 2026
  20. 0/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 22, 2026
  21. Mirko FainaApr 22, 2026
  22. 0/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 23, 2026
  23. 2/2 revision.c: reduce memory usage on reverse beforeMirko Faina, Apr 23, 2026
  24. 1/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 23, 2026
  25. Junio C HamanoApr 28, 2026
  26. 0/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 27, 2026
  27. 2/2 revision.c: reduce memory usage on reverse beforeMirko Faina, Apr 27, 2026
  28. Junio C HamanoApr 28, 2026
  29. 1/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 27, 2026
  30. Junio C HamanoApr 27, 2026
  31. Johannes SixtApr 27, 2026
  32. Junio C HamanoApr 27, 2026
  33. Chris TorekApr 27, 2026
  34. Mirko FainaApr 27, 2026
  35. Junio C HamanoApr 28, 2026
  36. Junio C HamanoApr 28, 2026
  37. revision.c: implement --max-count-oldestMirko Faina, Apr 30, 2026
  38. Junio C HamanoMay 4, 2026
  39. Mirko FainaMay 4, 2026
  40. revision.c: implement --max-count-oldestMirko Faina, May 5, 2026
  41. Johannes SixtMay 6, 2026
  42. Mirko FainaMay 6, 2026
  43. Junio C HamanoMay 7, 2026
  44. Mirko FainaMay 8, 2026
  45. Jean-Noël AVILAMay 9, 2026
  46. Mirko FainaMay 10, 2026
  47. Junio C HamanoMay 9, 2026
  48. Mirko FainaMay 10, 2026
  49. revision.c: implement --max-count-oldestMirko Faina, May 15, 2026
  50. revision.c: implement --max-count-oldestMirko Faina, May 19, 2026
  51. Mirko FainaMay 19, 2026
  52. Junio C HamanoMay 20, 2026
  53. Mirko FainaMay 20, 2026
  54. revision.c: implement --max-count-oldestJunio C Hamano, Jun 1, 2026
  55. Mirko FainaJun 2, 2026
  56. Junio C HamanoMay 19, 2026
  57. Mirko FainaMay 19, 2026
  58. Junio C HamanoMay 9, 2026
  59. Mirko FainaMay 10, 2026
  60. 2/2 revision.c: reduce memory usage on reverse beforeMirko Faina, Apr 22, 2026
  61. 1/2 revision.c: implement --reverse=before for walksMirko Faina, Apr 22, 2026
  62. Jeff KingApr 22, 2026
  63. Mirko FainaApr 22, 2026

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